It is known that, among vitamins, vitamin P relates to the physiological functions of vitamin C in living bodies, for example, it relates to the hydroxylation reaction of proline and lysine required for the synthesis of collagen as a main ingredient of biological connective tissues, as well as to the redox reaction of reducing Fe+++ in cytochrome C into Fe++ and to the immuno-enhancing effect of leukocytosis; and plays an important role in the maintenance and promotion of the health of living bodies.
Hesperidin, also known as vitamin P, is a compound represented by the following Chemical Formula 1 with the hesperetin structure, where rutinose composed of rhamnose and glucose binds to hesperetin, and it is a form of flavonoid contained abundantly in pericarps of citrus fruits; further, it has been known and used since a long time ago as vitamin P having physiological functions of reinforcing capillaries, preventing bleeding, and regulating blood pressure; and extensively used, for example, in food products, cosmetics, pharmaceuticals, etc.

In addition to the use of hesperidin as a vitamin P-enriched agent as a mere nutrient, hesperidin, in view of its chemical structure and physiological functions, can be incorporated alone or in combination with other vitamins into food products as an antioxidant, stabilizer, quality-improving agent, ultraviolet-absorbing agent, etc; pharmaceuticals such as prophylactic and therapeutic agents, i.e., agents for hesperidin-susceptive diseases such as hesperidin-susceptive viral diseases, bacterial diseases, circulatory diseases, and malignant tumors; and even into cosmetics such as skin-beautifying agents, skin-whitening agents, and anti-aging agents as a stabilizer, antioxidant, ultraviolet-absorbing agent, and melanin-formation inhibitory agent. Thus, hesperidin is used quite extensively.
However, since hesperidin hardly dissolves in water at a mere concentration of about one gram in 50 L of water (or about 0.002 w/v %) at ambient temperature, it has a severe difficulty in use.
As a means for improving the above problem, for example, Patent Literature 1 discloses α-glycosyl hesperidin, prepared by allowing a saccharide-transferring enzyme (or glycosyltransferase) to act on a solution containing hesperidin and a partial starch hydrolyzate, having a relatively-high water solubility, and being easily hydrolyzed in vivo to exert the physiological functions inherent to hesperidin without fear of inducing any toxicity, and a method for producing the same.
As a representative example of α-glycosyl hesperidin, α-glucosyl hesperidin, known as an enzyme-treated hesperidin, saccharide-transferred/glycosyl hesperidin, water-soluble hesperidin, or saccharide-transferred/glycosyl vitamin P, is a compound shown in the following Chemical Formula 2, wherein one molar glucose is bound to the glucose in the rutinose structure of hesperidin via α-bonding, and it is commercialized as a product containing the same as a main ingredient, for example, “HAYASHIBARA HESPERIDIN® S”, a product name of a glucosyl hesperidin, commercialized by Hayashibara Co., Ltd., Okayama, Japan.

It is known that conventional products, containing α-glycosyl hesperidin, contain concomitant hesperidin known as a causative production material for reducing the water solubility of α-glycosyl hesperidin; and, as a trial to improve the above reduction, a conversion of hesperidin into 7-O-β-glucosyl hesperetin, as shown in the following Chemical Formula 3, which is obtainable by releasing the rhamnose residue that constitutes the rutinose structure of hesperidin and has a distinctly-higher water solubility than hesperidin. For example, Patent Literature 2 discloses a method for producing an α-glycosyl hesperidin high content product with an improved water solubility by allowing α-L-rhamnosidase (EC 3. 2. 1. 40) to act on a solution containing hesperidin along with α-glucosyl hesperidin at a relatively high concentration to convert hesperidin into 7-O-β-glucosyl hesperetin and to reduce the content of the remaining hesperidin.

Products containing glycosyl hesperetins, i.e., what are called glycosyl hesperetins such as conventional hesperidin, α-glucosyl hesperetin, and 7-O-β-glucosyl hesperetin (may be simply called “conventional products”, hereinafter), have a specific bitterness (including roughness, harshness, or astringency) and an unfavorable aftertaste, i.e., a miscellaneous taste; there is disclosed, for example, in Patent Literature 3, a method of adding malic acid to beverages containing α-glycosyl hesperidin, i.e., glycosyl hesperetin, also known as a water-soluble hesperidin, as a method of improving the above defect.
However, even now, there has not yet been provided any glycosyl hesperetin product, whose miscellaneous tastes characteristic of conventional products have been improved to a fully satisfactory level.